Yes, but if you're talking about running costs, you're using around a 5th of the power of the AMD rig.
Did the same calculation myself about 6 weeks ago when I was looking to supplement my existing rigs. I had a choice of buying 6 750Ti's pulling 350W max, on a 650W power supply. Maximum cost for me £1000 (about $1500). For the R9 290x I was looking to duplicate what I had for my existing 290x rig. Two 1300W power supplies and a total cost of £2-2500 (about $4000). Total current draw 2200W. I'm paying for my electricity so it's a no brainer.
The point isn't necessarily high hashrate, it's to lower the associated costs you have to get that hashrate. As an example, there's no point having 3000 kHash if you make very little, or worse, a loss when you get that rate. These days with the pending growth in the use of ASICs it's better to look at the return for the investment you're putting in. If that takes 3 rigs, then so be it.
Thanks for the useful advice